In an effort to calm regulators' concerns about practices at the facility where it makes wires that connect defibrillators to the heart, St. Jude Medical Inc. has sent a letter to the U.S. Food and Drug Administration explaining improvements it says will be made.

The letter details efforts to correct problems found at the Sylmar, Calif., facility that makes St. Jude's Durata leads.

St. Jude's 34-page letter was made public Wednesday. It was a response to an October inspection of the Sylmar facility, after which the FDA had issued St. Jude a Form 483, a report detailing alleged violations it found during its inspection.

In a letter to the FDA, Philip Tsung, St. Jude vice president of quality assurance, wrote: "We recognize and take seriously the observations in the FDA-483, and are committed to taking all actions necessary to address them as part of our effort to continuously strengthen our quality system."

The Form 483 cited multiple quality-control concerns over such things as the number of tests performed on Durata leads and the facility's record-keeping. In a detailed response to the FDA sent Nov. 7, St. Jude acknowledged a need to improve its processes and promised to make changes and bolster training. It detailed planned and completed improvements.

In a statement Wednesday, the Little Canada-based medical technology company assured the FDA it "takes quality and product safety very seriously." St. Jude stressed that the FDA's concerns "centered on the company's internal quality system processes. It is important to note that none of the observations identified any specific issues with the clinical or field performance of any St. Jude Medical products."

The company said it is working closely with the FDA to "resolve the observations identified during these inspections."

Warning letter possible

St. Jude's share price fell nearly 13 percent in November after it was discovered that the FDA had raised concerns over processes concerning the Durata lead. St. Jude officials had earlier disclosed that they could receive a warning letter from the FDA over the Sylmar facility, but did not say those concerns involved Durata. A warning letter could lead to further problems for the company, such as a recall or a delay in getting other products approved, but such steps are uncommon.

An earlier lead made by St. Jude, called the Riata, was pulled from the market in late 2010 -- and was later classified as recalled by the FDA -- because of safety concerns. Analysts and physicians have said the market is skittish about any hint of trouble involving the Durata lead.

All along, St. Jude officials have stood by their data showing Durata has an excellent safety record. The next step -- following St. Jude's response to the FDA -- remains to be seen. The FDA could reinspect the facility. It could also issue a warning letter before or after re-inspection. If a warning letter comes, it would probably arrive in the next few months.

FDA's next step?

Ron Johnson has worked as a consultant to St. Jude Medical and is a former FDA compliance official. He worked at the FDA for 30 years, but in a recent interview said he's unsure sure what regulators will do next.

There are enough concerns listed in the Form 483 that "a warning letter is warranted," he said. But even the impact of that is not certain. A re-inspection is almost a certainty. But while the FDA could decide to delay approval of any new St. Jude devices until its Sylmar concerns are addressed, Johnson said such a move is rare. In fact, he said, companies often continue conducting business as usual during the process.

"That is usually the most draconian feature of a warning letter," Johnson said of a hold the FDA could impose.

Even if a warning letter is issued, he said, it may mean little to the prospects for the Durata lead overall.

According to Johnson, the FDA issues hundreds of warning letters every year and most of those never lead to a product recall. He said he does not expect a recall involving Durata.

"If FDA is really worried, if they think a recall needs to happen, that would be happening pretty soon," Johnson said.

On Wednesday, St. Jude's stock finished the day at $37.30, up less than 1 percent.

In preliminary fourth-quarter results announced Wednesday in San Francisco, St. Jude said profit was 90 to 92 cents a share in the quarter ended Dec. 29, excluding 50 to 60 cents a share from one-time items such as restructuring costs and other charges. Earnings topped the average of 87 cents from 25 analysts' estimates compiled by Bloomberg.